From 5d3869a41f3608101c00ff9c9c7c2364c555fa65 Mon Sep 17 00:00:00 2001 From: Olga Kornievskaia Date: Mon, 13 Apr 2026 18:24:23 -0400 Subject: NFS: fix writeback in presence of errors After running xfstest generic/751, in certain conditions, can have a writeback IO stuck while experiencing one of the two patterns. Pattern#1: writeback IO experiences ENOSPC on an offset smaller than the filesize. Example, write offset=0 len=4096 how=unstable OK write offset=8192 len=4096 how=unstable OK write offset=12288 len=4096 how=unstable ENOSPC write offset=4096 len=4096 how=unstable ENOSPC client sends a commit and receives a verifier which is different from the last successful write. It marks pages dirty and writeback retries. But it again send writes unstable and gets into the same pattern, running into the ENOSPC error and sending a commit because writes were sent at unstable. Pattern#2: an unstable write followed by a short write and ENOSPC. write offset=0 len=4096 how=unstable OK write offset=4096 len=4096 how=unstable returns OK but count=100 write offset=4197 len=3996 how=stable returns ENOSPC client send a commit and receives a verifier different from the last unstable write. The same behaviour is retried in a loop. Instead, this patch proposes to identify those conditions and mark requests to be done synchronously instead. Previous solution tried to mark it in the nfs_page, however that's not persistent thus instead mark it in the nfs_open_context. Furthermore, the same problem occurs during localio code path so recognize that IO needs to be done sync in that case as well. Signed-off-by: Olga Kornievskaia Signed-off-by: Trond Myklebust --- include/linux/nfs_fs.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h index 8dd79a3f3d66..4623262da3c0 100644 --- a/include/linux/nfs_fs.h +++ b/include/linux/nfs_fs.h @@ -109,6 +109,7 @@ struct nfs_open_context { #define NFS_CONTEXT_BAD (2) #define NFS_CONTEXT_UNLOCK (3) #define NFS_CONTEXT_FILE_OPEN (4) +#define NFS_CONTEXT_WRITE_SYNC (5) struct nfs4_threshold *mdsthreshold; struct list_head list; -- cgit v1.2.3